Malignant mesothelioma diagnosed at a younger age is associated with heavier asbestos exposure

Our plain-English summary of Malignant mesothelioma diagnosed at a younger age is associated with heavier asbestos exposure, by T.A. Dragani, F. Colombo, E.N. Pavlisko, et al (Carcinogenesis, 2018).

The study

• Authors: T.A. Dragani, F. Colombo, E.N. Pavlisko, V.L. Roggli
• Journal: Carcinogenesis
• Published: 2018;39(9):1151-1156
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos exposure is the main etiology of malignant mesothelioma, but there are conflicting data on whether the intensity of exposure modulates the development of this disease. This study considered 594 patients with malignant mesothelioma for whom count data on asbestos bodies and fibers (per gram of wet lung tissue) were available. The relationships between age at diagnosis (a time-to-event outcome variable) and these two measures of internal asbestos exposure, along with other possible modulating factors (sex, tumor location, histological subtype and childhood exposure), were assessed on multivariable Cox proportional hazard models, stratifying by decade of birth year. For both measures of asbestos in lung tissue, younger age at diagnosis was associated with higher internal measures of exposure to asbestos. Stratified Cox analyses showed that for each doubling in asbestos body count patients were 1.07 times more likely to be diagnosed at a younger age [hazard ratio (HR) = 1.07; 95% confidence interval (CI), 1.04-1.09; P = 2.2 × 10-7] and for each doubling in asbestos fiber count patients were 1.13 times more likely to be diagnosed at a younger age (HR = 1.13; 95% CI, 1.09-1.17; P = 8.6 × 10-11). None of the other variables considered were associated with age at diagnosis. Our finding that tumors become clinically apparent at a younger age in heavily exposed subjects suggests that asbestos is involved not only in the malignant mesothelioma tumor initiation but, somehow, also in the progression of the disease.

In plain English

This study looked at 594 patients diagnosed with malignant mesothelioma at Duke University Medical Center between 1982 and 2017, all with laboratory counts of asbestos in their lung tissue. The authors counted asbestos bodies by light microscopy and asbestos fibers by scanning electron microscopy, with all fiber types added together. They asked whether patients with more asbestos in their lungs were diagnosed younger. The analyses were split by decade of birth and took sex, tumor location, tissue subtype and childhood exposure into account. Across all patients, each doubling of asbestos body count went with being 1.07 times more likely to be diagnosed at a younger age (HR 1.07; 95% CI 1.04 to 1.09). Each doubling of fiber count went with 1.13 times (HR 1.13; 95% CI 1.09 to 1.17). None of the other factors was associated with age at diagnosis. The authors concluded that asbestos may be involved not only in starting the tumor but, somehow, also in its progression. They noted that only diagnosed patients were studied, not exposed people without the disease.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Case series of mesothelioma patients with lung asbestos counts, analyzed with multivariable Cox regression of age at diagnosis, stratified by decade of birth
• Who was studied: 594 patients diagnosed with malignant mesothelioma at Duke University Medical Center (Durham, NC), 1982 to 2017, with lung asbestos body or fiber counts available. Asbestos body counts were available for 587 and fiber counts for 577. 509 (85.7%) were men; 549 (92.4%) had pleural and 41 (6.9%) peritoneal tumors.
• Exposure: Asbestos lung burden: asbestos bodies counted by light microscopy and asbestos fibers counted by scanning electron microscopy, with all fiber types added together, per gram of wet lung tissue. Specific fiber types are not reported separately. Occupational and childhood exposure were estimated from self-reported job type and sector of activity.
• Main results:
  • Patients were diagnosed between ages 25 and 94, median 65 years.
  • The 367 patients with occupational exposure had higher lung asbestos levels than the 139 patients without such exposure.
  • All patients, stratified by birth decade: for each doubling in asbestos body count, patients were 1.07 times more likely to be diagnosed at a younger age (HR = 1.07; 95% CI, 1.04 to 1.09; P = 2.2 × 10^-7).
  • All patients, stratified by birth decade: for each doubling in asbestos fiber count, patients were 1.13 times more likely to be diagnosed at a younger age (HR = 1.13; 95% CI, 1.09 to 1.17; P = 8.6 × 10^-11).
  • Within individual birth cohorts, significant associations were found only in cohorts born 1921–1930, 1931–1940 and 1941–1950. These were the largest cohorts, and in them higher counts went with diagnosis at a younger age.
  • Sex, tumor location, histological subtype and childhood exposure were not associated with age at diagnosis.
• The authors' conclusion: The authors concluded that heavily exposed patients were diagnosed at a younger age. In their view, this suggests asbestos is involved not only in starting the tumor but, somehow, also in disease progression. They proposed that inflammation from high asbestos levels could plausibly be the reason.
• Limitations the authors state:
  • The study assessed age at diagnosis only in people diagnosed with mesothelioma, not in exposed people not yet diagnosed. The authors argued that case-only analyses are nonetheless valid.
  • The lack of association with childhood exposure may be due to the small number of such cases (5% of the total).

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Asbestos Exposure, Etiology, Asbestos Bodies, Histological Subtype, Asbestos Body Formation, Hazard Ratio, confidence interval.

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